Quantum spill-out in few-nanometer metal gaps

Effect on gap plasmons and reflectance from ultrasharp groove arrays

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a quantum mechanical approach and assuming local response, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves.We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1–2 °A from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be in
much better agreement with measurements compared with classical models.
Original languageEnglish
Article number115429
JournalPhysical Review B
Volume97
Issue number11
Pages (from-to)1-9
Number of pages9
ISSN2469-9950
DOIs
Publication statusPublished - 19 Mar 2018

Cite this

@article{74701c3c1dfd4b1f8e50e9319c6318e9,
title = "Quantum spill-out in few-nanometer metal gaps: Effect on gap plasmons and reflectance from ultrasharp groove arrays",
abstract = "Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a quantum mechanical approach and assuming local response, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves.We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1–2 °A from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be inmuch better agreement with measurements compared with classical models.",
keywords = "Gap plasmons, Mode index, Electron spill-out, Density functional theory, Ultrasharp grooves, Metal optics",
author = "Skj{\o}lstrup, {Enok Johannes Haahr} and Thomas S{\o}ndergaard and Pedersen, {Thomas Garm}",
year = "2018",
month = "3",
day = "19",
doi = "10.1103/PhysRevB.97.115429",
language = "English",
volume = "97",
pages = "1--9",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Physical Society",
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}

Quantum spill-out in few-nanometer metal gaps : Effect on gap plasmons and reflectance from ultrasharp groove arrays. / Skjølstrup, Enok Johannes Haahr; Søndergaard, Thomas; Pedersen, Thomas Garm.

In: Physical Review B, Vol. 97, No. 11, 115429, 19.03.2018, p. 1-9.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Quantum spill-out in few-nanometer metal gaps

T2 - Effect on gap plasmons and reflectance from ultrasharp groove arrays

AU - Skjølstrup, Enok Johannes Haahr

AU - Søndergaard, Thomas

AU - Pedersen, Thomas Garm

PY - 2018/3/19

Y1 - 2018/3/19

N2 - Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a quantum mechanical approach and assuming local response, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves.We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1–2 °A from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be inmuch better agreement with measurements compared with classical models.

AB - Plasmons in ultranarrow metal gaps are highly sensitive to the electron density profile at the metal surfaces. Using a quantum mechanical approach and assuming local response, we study the effects of electron spill-out on gap plasmons and reflectance from ultrasharp metal grooves.We demonstrate that the mode index of ultranarrow gap plasmons converges to the bulk refractive index in the limit of vanishing gap and, thereby, rectify the unphysical divergence found in classical models. Surprisingly, spill-out also significantly increases the plasmonic absorption for few-nanometer gaps and lowers the reflectance from arrays of ultrasharp metal grooves. These findings are explained in terms of enhanced gap plasmon absorption taking place inside the gap 1–2 °A from the walls and delocalization near the groove bottom. Reflectance calculations taking spill-out into account are shown to be inmuch better agreement with measurements compared with classical models.

KW - Gap plasmons

KW - Mode index

KW - Electron spill-out

KW - Density functional theory

KW - Ultrasharp grooves

KW - Metal optics

U2 - 10.1103/PhysRevB.97.115429

DO - 10.1103/PhysRevB.97.115429

M3 - Journal article

VL - 97

SP - 1

EP - 9

JO - Physical Review B

JF - Physical Review B

SN - 2469-9950

IS - 11

M1 - 115429

ER -